Silphenylene-siloxane fluids and method of preparation



3,332 973 SILPHENYLENE-SILO XANE FLUIDS AND METHOD OF PREPARATION -Rhert L. Merker, Pittsburgh, Pa., assignor to Dow Corning Corporation, Midland, Mich., a corporation of Michigan No Drawing..Filed Feb. 27, 1963, Ser. No. 261,514

6 Claims. (Cl. 260-4483) This invention relates to new fluid silphenylene-siloxane copolymers.

More particularly this invention relates to fluid silphenylene-sil-oxane copolymers having the average general forwherein each R is independently selected from the group consisting of methyl'and 3,3,3-trifluoropropyl radicals, a and b are integers such that the ratio of a to b is in the range from 1:1 to 12.5:1, said copolymers having viscosities from to 350,000 cs. at C. a

The fluid copolymers of this invention are useful, for example, as lubricants, dielectric coolants, damping and viscous drive fluids and as viscosity index improvers for silicate and other hydraulic fluids. The fluid copolymers of this invention are particularly useful at high temperatures because of their thermal stability and the fact that they combine thermal stability with a relatively small change in viscosity with changing temperature.

It should be understood that the various siloxane units can be arranged in any configuration within the limits set by the above average'formulae. For example, within any particular molecule, the R SiO and the silphenylene units can 'be arranged in a regular or in a random manner and the R Si-- and the R515 groups can be attached to either the R Si0 units or the, silphenyl units or to both types of 'said units.

' The compositions of this invention can be prepared in several ways. For example, one can equilibrate linear or cyclic R SiO polymers with linear or cyclic silphenylene polymers Duringthe equilibration R Si-- and RSlE units can be introduced by any convenient'procedure. If desired one can cocondense.

R SiX and RSiX "in which X is a hydroxyl reactive group such as acetoxy, alkoxy, etc. Fnally one can cohydrolyze the corresponding hydrolyzable silanes, i.e. R SiCl Ra Ra 'R SiCl and .if desired RSiCl All of these processes are 1 perature-of from to 190 C. for ;l0 to 35 hour-sin 3,332,973 Patented July 25, 1967 ICC the presence of an alkaline catalyst such as potassium hydroxide. It is preferred that a trimethylsilyl-endblock polydimethylsiloxane having a viscosity of 1 to 100 cs. at 25 C., a temperature of 140to 170 C. and a time of 15 to 30 hours be employed.

Any suitable alkaline catalyst can also be used. For example, the catalyst can be potassium hydroxide, sodium hydroxide, ammonium hydroxide, potassium dimethylsilanolate, etc.

The following examples are for the purpose of illustration only and should not be construed as limiting to the invention.

Example 1 a 247 g. of para-bis (dimethylhydroxysilyl)benzene, 265.5 g. of polydimethylsiloxane cyclics, 17.8 g. of a trimethylsiloxy-endblocked dimethylsiloxane fluid having a viscosity of 1.5 cs. at 25 (3., about 530 g. of dry toluene and one percent potassium hydroxide (catalyst) were added to a reaction vessel and refluxed for 16 hours at to 120 C. The catalyst was then neutralized with trimethylchlorosilane. The toluene and other low molecular weight materials were stripped from the fluid to 255 C. at a pressure of 1 mm. of mercury. The 452 g. of product obtained was treated with 2.5 g. of Nuchar (an activated charcoal) for 2 hours at 75 C. and then filtered thru Super-Cel (a di-atomaceous silica). The filtered product consisted of 397.3 g. of a fluid having a viscosity of 385.5 cs. at 25 C.

1 Example 2 219 g. of parabis(dimethylhydroxysilyl)benzene, 437.5 g. of polydimethylsiloxane cyclics, 20.4 g. of a trimethylsiloxy-endblocked dimethylsiloxane fluid having a viscosity of 1.5 cs. at 25 C., about 677 g. of toluene and 1 percent of optasium hydroxide were added to a reaction vessel and refluxed for 16 hours at 114 to 115 C. The fluid was then neutralized with 7.0 g. of trimethylchlorosilane. The toluene and low molecular weight materials were stripped from the fluid to 269 C. at a pressure of 1 mm. of mercury. The 546 g. of product obtained was treated with 5 g. of Nuchar for 2 hours at 70 to 75 C. and then filtered thru Super-Cel. The filtered product consisted of 490 g. of a fluid having a viscosity of 209.5 cs. at 25C.

Example 3 '113' g. of para-bis(dimethylhydroxysilyl)benzene, 200 g. of polydimethylsiloxane cyclics,124 g. of a trimethylsiloxy-endblocked dimethylsiloxane fluid having a viscosity of 1.5cs. at 25 C., 426 g. dry toluene and 4.3 g. of potassium hydroxide pellets were added to a reaction vessel andequilibrated for 18 hours at 110 to C. The fluid was then neutralized with 12g. of trimethylchlorosilane. The toluene and low molecular weight materials werestripped from the fluid to 250 C. at a pressure of 0.27 5. mm. of mercury. Then the product was treated with Nuchar and filtered. The filtered product consisted of 191.7 g. of a clear liquid having a viscosity of 36.6 cs. at 25 C. p

Example 4 226 g. of para-bis(dimethylhydroxysilyl)benzene, 163 g. of octamethylcyclotetrasiloxane, 124 g. of a trimethylsiloxy-endblocked dimethylsiloxane fluid having a viscosity of 1.5 cs. at 25 C. and 5.0 g. of potassium hydroxide pellets were placed in a reaction vessel and equilibrated for 24 hours at to C. The catalyst was then neutralized with 10 g. of trimethylchlorosilane. The fluid was stripped of low molecular weight materials to 275 C. at a pressure of 0.15 mm. of mercury. The product was treated with 3 g. of Nuchar and then filtered thru Super-Cel. The filtered product consisted of 207.7 g. of a clear liquid havinga viscosity of 59.5 cs at 25 C.

Example 5 452 g. of para-bis(dimethylhydroxysilyl) benzene, 326 g. of octamethylcyclotetrasiloxane, 248 g. of a trimethylsiloxy-endblocked dimethylsiloxane fluid having a viscosity of 1.5 cs. at 25 C. and g. of potassium hydroxide were added to a reaction vessel and equilibrated for 24 hours at 150 to 160 C. Thefluid was then neutralized with 120 g. of trimethylchlorosilane. The low molecular Weight materials were stripped from the fluid to 335 C. at a pressure of 0.7 to 0.8 mm. of mercury. Nuc'har was added to the fluid and it was filtered hot. 755 g. of a slight ly hazy fluid was obtained. The fluid was then chilled with Dry Ice and filtered thru Super-Col. The product had a viscosity of 142.6 cs. at 25 C.

Example 6 338 g. of para-bis(dimethylhydroxysilyl)benzene, 771 g. of polydimethylsiloxane cyclics, 7.5 g. of a trimethyl- ;iloxy-endblocked dimethylsiloxane fluid having a viscosity of 5 cs. at 25 C. and 10 g. of the potassium salt of golydimethylsilanolate were added to a reaction vessel and heated for about 24 hours at 150 to 160 C. The fluid was then diluted with toluene, neutralized with Dry Ice and filtered. The toluene and other volatiles were stripped "rem the fluid in two stages, the first stage being to 170 1. at a pressure of 28 mm. of mercury and the second :tage being to 300 C. at a pressure of 1 mm. of mercury. [he 964 g. of product obtained was a fluid having a viscosty of about 5000 (i.e. 4959) cs. at 25 C.

Example 7 559 g. of para-bis(dimethyl-hydroxysilyl)benzene 1287 c. of polydimethylsiloxane cyclics, 27 g. of a trimethyliloxy-endblocked dimethylsiloxane fluid having a viscosty of 5 cs. at 25 C. and 18 g. of the potassium salt of lolydimethylsilanolate were added to a reaction vessel nd heated for about 20 hours at 150 C. The fluid then 738 cooled, diluted with toluene, neutralized with Dry cc and filtered. The toluene and other volatiles were tripped from the fluid in two stages, the first stage being a 175 C. at a pressure of 25 mm. of mercury and the econd stage being to 304 C. at a pressure of 0.1 mm. of iercury. The 1230 g. of product obtained was a fluid avinga viscosity of 15,300 cs. at 25 C.

Example 8 This example illustrates the fact that the fluid silphenylne-siloxane copolymers of this invention have better lermal stability at high temperatures than similar fluids Jntaining only methyl groups.

The thermal stability test consisted of heating the uids, under nitrogen, in an oven at 250 C. for 24 hours. he viscosities of the fluids were measured at 25 C. both :fore and after they were heated in the oven. The fluid lmples were prepared for the oven by placing them in a the, evacuating the air from the tube, purging with nitrom and then sealing the tube. The silphenylene-siloxane uid used in the test was that of Example 6. The test rellts are set forth below and show that the percent change the viscosity of the polydimethylsiloxane fluid was more ran twice as great as the change in the viscosity of the lphenylene-siloxane fluid of this invention.

62.5 g. of a hydroxyla-ted polydimethylsiloxane fluid wing a degree of polymerization of about 18. 62.5 2. of

para-bis(dimethylhydroxysilyl)benzene and 31 cc. tetrahydrofuran were refluxed until the monomers had' dissolved. Then 22.4 g. of trirnethylacetoxysilane was added and the mixture refluxed 2% hours. Then, after the addition of 0.6 g. of tetramethylguanidine-di-Z-ethylhexoate, the mixture was refluxed for one more hour. The mixture was then diluted with benzene and the acetic acid washed out with water. The benzene was then distilled off, and 0.10 percent by weight KO'H, based on the monomers, was added. After removal of the water azeotrop'e, the mixture was refluxed for 2% hours. The reaction products were washed with water, dried over Na SO and then filtered. The product was clear and colorless and had a viscosity of 91 cs. at 25 C. The product was tested for thermal stability as above except that it was heated for 8 hours at 800 F. Before heating the fluid had a viscosity of 19.2 cs. at 210 F. After heating it was found to have a viscosity of 18.6 cs. at 210 F. This is a change in viscosity of only 3.1 percent.

Example 10 When an equivalent amount of bis(3,3,3-trifluoropropyl)siloxane cyclics are substituted for the dimethylsiloxane cyclics of Example 1, a silphenylene-siloxane copolymer fluid is obtained which. contains 3,3,3-trifluoropropyl groups.

Example 11 When the desired ratios of CH Si[OSi( CI-I [(CH SiO] and are equilibrated in the presence of an alkaline catalyst at silphenylene-siloxane copolymer fluid having the average general formula Sl]bOSl(C a)ala is obtained.

That which is claimed is:

1. Silphenylene-siloxane. copolymers having the average general formula I l I RaSi(OSl) .(osr-O-sn bosuz,

and' wherein each R is independently selected from the group consisting of methyl and 3,3,3-trifluoropropyl radicals, a and b are integers such that the ratio of a to b is in the range from 1:1 to 12.521, said copolymers having viscosities in the range from 15 to 350,000 cs. at 25 C.

2. The silphenylene-siloxane copolymers of claim 1 having the average general formula R: R2 RI 3. The silphenylene-siloxane copolymers of claim 2 wherein the ratio of a to b is'in the range from 3:1 to 7: 1.

4. The silphenylene-siloxane copolymers of claim 2 wherein all of the groups are methyl radicals.

5. The silphenylene-siloxane copolymers of claim 2 wherein the R groups are a mixture of methyl and 3,3,3- trifiuoropropyl radicals.

6. The method for preparing silphenylene-siloxane copolymers having the average general formula 2) 2 1 2 R3s1 osi 1 osrQ-sr bosim wherein each R is independently selected from the group consisting of methyl and 3,3,3-trifluoropropyl radicals, a and b are integers such that the ratio of a to b is in the range from 1:1 to 12.5 :1, said method comprising equilibrating a mixture consisting of para-bis(dimethy1 hydroxysilyDbenzene, at least one cyclic selected from the group consisting of dimethylsiloxane cyclics, bis- (3,3,3-trifluor0propyl)-siloXane cyclics and (methyl) 3,3,3-trifiuoropropylsiloxane cyclics and a trimethylsilylendblocked dimethylsiloxane fluid having a viscosity of 6 from 0.65 to 300,000 cs. at C. at a temperature of from to C. for 10 to 35 hours in the presence of an alkaline catalyst, whereby a fluid having a viscosity in the range from 15 to 350,000 cs. at 25 C. is obtained References Cited UNITED STATES PATENTS TOBIAS E. LEVOW,

SAMUEL H. BLECH, HELEN M. MCCARTHY, P. F.

SHAVER, Assistant Examiners.

Primary Examiner. 

1. SILPHENYLENE-SILOXANE COPOLYMERS HAVING THE AVERAGE GENERAL FORMULA 